Average Follow-up Time DetailBecause of the historical cohort design, no exact follow-up time was available. Participants were World WarII US Navy or Marine male veterans who had served during 1944 to 1945. Abstraction of medical records occurred in 1996 to 1997, which was then followed by participant recruitment and dementia assessment.

Exposure DetailHistory of head injury was ascertained from a review of military medical records.

"Trained staff abstracted the militarymedical records for information about the headinjuries, including cause of injury and duration of loss ofconsciousness or post-traumatic amnesia. Men were thenconsidered “exposed” if they had experienced head traumathat 1) was documented in the military medical records,2) occurred during military service, 3) produced loss ofconsciousness, post-traumatic amnesia, or skull fracture,4) did not penetrate the dura mater, and 5) did not resultin marked cognitive impairment or neurologic sequelaemore than 3 months post-trauma."

The severity of the head injuries were also categorized as follows: "1) mild injury 5 loss of consciousness or post-traumatic amnesia for less than 30 minutes, with no skull fracture; 2) moderate injury 5 loss of consciousness or post-traumatic amnesia for more than 30 minutes but less than 24 hours, and/or a skull fracture; and 3) severe injury 5 loss of consciousness or post-traumatic amnesia for more than 24 hours."

The investigators examined both any head injury with loss of consciousness and severity of head injury. This entry is for any head injury with loss of consciousness.

Age DetailAge at start of follow-up was not available.

Screening and Diagnosis DetailScreening Method:

DQ

Dementia Questionnaire (Silverman 1986)

IQ-CODE

Informant Questionnaire for Cognitive Decline in the Elderly (Jorm 1989)

Men with dementia were identified in three stages. First, the TICS was administered, or the IQ-CODE to an informant when the participant was unable to be tested. Men with aneducation-adjusted TICS score of less than 29 or anIQCODE score above 3.2719 were then screened using the Dementia Questionnaire (DQ). Men whose DQ results suggested dementia to then underwent a clinical assessment administered by a research nurse and psychometrician. Diagnoses of AD were made using NINCDS-ADRDA criteria by aboard-certified geriatric psychiatrist, a cognitive neuroscientist, and the assessment team.